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          LV06-03-网络编程-10-广播与多播
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              <table>    <tr>        <td align="center" width=150px>Windows</td>        <td align="left">windows11</td>    </tr>    <tr>        <td align="center">Ubuntu</td>        <td align="left">Ubuntu16.04的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 16 Pro</td>        <td align="left">16.2.3 build-19376536</td>      </tr>    <tr>        <td align="center">SecureCRT</td>        <td align="left">Version 8.7.2 (x64 build 2214)   -   正式版-2020年5月14日</td>      </tr>    <tr>        <td align="center">开发板</td>        <td align="left">正点原子 i.MX6ULL Linux阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，NXP提供的版本为uboot-imx-rel_imx_4.1.15_2.1.0_ga(使用的uboot版本为U-Boot 2016.03)</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.15(NXP官方提供)</td>      </tr>    <tr>        <td align="center">STM32开发板</td>        <td align="left">正点原子战舰V3(STM32F103ZET6)</td>      </tr></table>
              </div>
            </details>

<details class="folding-tag" blue><summary> 点击查看本文参考资料 </summary>
              <div class='content'>
              <table>    <tr><td align="center">参考方向  </td><td align="center">参考原文</td></tr>    <tr><td align="center">---</td><td align="left"><a href="" target="_blank">--- <i class="fa fa-external-link-alt"></i> </a></td></tr></table>
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<details class="folding-tag" blue><summary> 点击查看相关文件下载 </summary>
              <div class='content'>
              <table>    <tr>        <td align="center">---</td>        <td align="left">--- <a href="" target="_blank">  <i class="fa fa-external-link-alt"></i></a></td>      </tr></table>
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<h1 id="一、广播编程"><a href="#一、广播编程" class="headerlink" title="一、广播编程"></a><font size=3>一、广播编程</font></h1><h2 id="1-广播的概念"><a href="#1-广播的概念" class="headerlink" title="1. 广播的概念"></a><font size=3>1. 广播的概念</font></h2><p>在前面介绍的数据包发送方式只有一个接受方，称为<strong>单播</strong>，那什么叫广播呢？<strong>广播</strong>（<code>broadcast</code>）是指封包在计算机网络中传输时，<strong>目的地址为网络中所有设备的一种传输方式</strong>。实际上，这里所说的“所有设备”也是限定在一个范围之中，称为<strong>广播域</strong>。</p>
<p>也就是说，如果<strong>同时发给局域网中的所有主机</strong>，称为广播。需要注意的是<strong>只有用户数据报(使用UDP协议)套接字才能广播</strong>。</p>
<h2 id="2-广播的缺点"><a href="#2-广播的缺点" class="headerlink" title="2. 广播的缺点"></a><font size=3>2. 广播的缺点</font></h2><ul>
<li>无法针对每个客户的要求和时间及时提供个性化服务。</li>
<li>网络允许服务器提供数据的带宽有限，客户端的最大带宽＝服务总带宽。例如有线电视的客户端的线路支持<code>100</code>个频道（如果采用数字压缩技术，理论上可以提供<code>500</code>个频道），即使服务商有更大的财力配置更多的发送设备、改成光纤主干，也无法超过此极限。也就是说无法向众多客户提供更多样化、更加个性化的服务。</li>
<li>广播禁止在<code>Internet</code>宽带网上传输。</li>
</ul>
<h2 id="3-广播分类"><a href="#3-广播分类" class="headerlink" title="3. 广播分类"></a><font size=3>3. 广播分类</font></h2><p> 广播分为两种，<strong>直接广播</strong>和<strong>本地广播</strong>（也叫受限广播），两者的主要差别如下</p>
<ul>
<li>目标网络方面</li>
</ul>
<p>直接广播的目标网络和发送端不在同一个网络，本地广播的目标网络就是发送端本机所在的网络。</p>
<ul>
<li><code>IP</code>地址方面</li>
</ul>
<p>直接广播的<code>IP</code>地址，除了网络地址外，其余主机地址全部设置为<code>1</code>.如希望向网络地址<code>192.168.5</code>的所有主机传输数据时，发送端的目标<code>IP</code>要设置为<code>192.168.5.255</code>传输。而本地广播中使用的<code>IP</code>地址限定为<code>255.255.255.255</code>。</p>
<p>需要注意的是<strong>本地广播只能在局域网内转发</strong>，主要用于不知道目标主机的掩码与网络地址的情况，本地转发同本地网络下的所有主机。</p>
<h2 id="4-广播地址"><a href="#4-广播地址" class="headerlink" title="4. 广播地址"></a><font size=3>4. 广播地址</font></h2><p>其实上边已经提过了，主机地址全部为<code>1</code>的地址就是该网段的广播地址。以<code>192.168.1.0</code> (<code>255.255.255.0</code>) 网段为例，最大的主机地址<code>192.168.1.255</code>代表该网段的广播地址，发到该地址的数据包被所有的主机接收。</p>
<p><strong>【注意】</strong><code>255.255.255.255</code>在所有网段中都代表广播地址。</p>
<h2 id="5-广播编程步骤"><a href="#5-广播编程步骤" class="headerlink" title="5. 广播编程步骤"></a><font size=3>5. 广播编程步骤</font></h2><div class="tabs" id="tabname1"><ul class="nav-tabs"><li class="tab active"><a href="#tabname1-1">广播发送</a></li><li class="tab"><a href="#tabname1-2">广播接收</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname1-1"><ul>
<li>创建用户数据报套接字，注意<code>soclet()</code>函数第二个参数要写为<code>SOCK_DGRAM</code>。</li>
<li>设置网络属性，允许广播数据包，这是因为默认的情况下创建的套接字是不允许广播数据包的。</li>
<li>接收方地址指定为广播地址。</li>
<li>指定端口信息。</li>
<li>发送数据包。</li>
</ul></div><div class="tab-pane" id="tabname1-2"><ul>
<li>创建用户数据报套接字，注意<code>soclet()</code>函数第二个参数要写为<code>SOCK_DGRAM</code>。</li>
<li>绑定本机<code>IP</code>地址和端口，绑定的端口必须和发送方指定的端口相同。</li>
<li>等待接收数据。</li>
</ul></div></div></div>

<h2 id="6-使用实例"><a href="#6-使用实例" class="headerlink" title="6. 使用实例"></a><font size=3>6. 使用实例</font></h2><h3 id="6-1-server服务器端"><a href="#6-1-server服务器端" class="headerlink" title="6.1 server服务器端"></a><font size=3>6.1 <code>server</code>服务器端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: server.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: server服务器端——广播(UDP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>      <span class="comment">/* perror */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>     <span class="comment">/* exit atoi */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>      <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span>  <span class="comment">/* socket           bind listen recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span> <span class="comment">/* socket inet_addr bind listen recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;strings.h&gt;</span>    <span class="comment">/* bzero */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span>  <span class="comment">/* htons  inet_addr inet_pton */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span> <span class="comment">/* ntohs  inet_addr inet_ntop*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>     <span class="comment">/* close */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>     <span class="comment">/* strlen strcat*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 1.参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">3</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 2.创建套接字，得到socket描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span>((socket_fd = socket(AF_INET, SOCK_DGRAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)<span class="comment">/* SOCK_STREAM,使用TCP协议 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 3.网络属性设置 */</span></span><br><span class="line">	<span class="comment">/* 3.1允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 4.将套接字与指定端口号和IP进行绑定 */</span></span><br><span class="line">	<span class="comment">/* 4.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>));  <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;    <span class="comment">/* 协议族, IPv4 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port);  <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* 填充IP地址,INADDR_ANY表示允许监听任意IP,但是它其实是(in_addr_t) 0x00000000 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 4.2绑定 */</span></span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;Boardcast server starting....OK(UDP)!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 5.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="comment">/* 5.2客户端IP地址及端口号获取的相关变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">cin</span>;</span>          <span class="comment">/* 用于存储成功连接的客户端的IP信息 */</span></span><br><span class="line">	<span class="type">socklen_t</span> addrlen = <span class="keyword">sizeof</span>(<span class="built_in">cin</span>);</span><br><span class="line">	<span class="type">char</span> ipv4_addr[<span class="number">16</span>];</span><br><span class="line">	<span class="comment">/* 5.2数据读写相关变量 */</span></span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="comment">/* 6.数据读写 */</span></span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 6.1接收来自客户端的数据 */</span></span><br><span class="line">		bzero(buf, BUFSIZ);</span><br><span class="line">		<span class="keyword">if</span>(recvfrom(socket_fd, buf, BUFSIZ<span class="number">-1</span>, <span class="number">0</span>,(<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">cin</span>, &amp;addrlen ) &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;recvfrom&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.2打印客户端的IP信息 */</span></span><br><span class="line">		<span class="keyword">if</span> (!inet_ntop (AF_INET, (<span class="type">void</span> *) &amp;<span class="built_in">cin</span>.sin_addr, ipv4_addr, <span class="keyword">sizeof</span> (<span class="built_in">cin</span>)))</span><br><span class="line">		&#123;</span><br><span class="line">			perror (<span class="string">&quot;inet_ntop&quot;</span>);</span><br><span class="line">			<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;Recived from(%s:%d), data:%s&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port), buf);</span><br><span class="line">		<span class="comment">/* 6.3判断是否需要退出 */</span></span><br><span class="line">		<span class="keyword">if</span>(!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span>(<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">printf</span> (<span class="string">&quot;Client(%s:%d) is exiting!\n&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port));</span><br><span class="line">			<span class="comment">// break;</span></span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 7.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s serv_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t Attention: The IP address must be the IP address of the local nic or 0.0.0.0 \n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="6-2-client客户端"><a href="#6-2-client客户端" class="headerlink" title="6.2 client客户端"></a><font size=3>6.2 <code>client</code>客户端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: cilent.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: client客户端程序——广播(UDP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>     <span class="comment">/* perror fgets */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>    <span class="comment">/* exit atoi*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>     <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>    <span class="comment">/* write close */</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span> <span class="comment">/* socket           recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span><span class="comment">/* socket inet_addr recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span><span class="comment">/* inet_addr */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span> <span class="comment">/* inet_addr inet_pton htonl*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>   <span class="comment">/* bzero strncasecmp strlen */</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 主函数 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 1.参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">3</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 2.打开套接字，得到套接字描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span> ((socket_fd = socket(AF_INET, SOCK_DGRAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 3.网络属性设置 */</span></span><br><span class="line">	<span class="comment">/* 3.1允许广播设置 */</span></span><br><span class="line">	<span class="type">int</span> b_br = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_BROADCAST, &amp;b_br, <span class="keyword">sizeof</span>(<span class="type">int</span>));</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 4.连接服务器 */</span></span><br><span class="line">	<span class="comment">/* 4.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="comment">/* 客户端的 argv[1] 需要与系统的IP一致 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;Broadcast client staring...OK(UDP)!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 5.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="comment">/* 6.数据读写 */</span></span><br><span class="line">	<span class="keyword">while</span> (<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 6.1标准输入获取发送数据 */</span></span><br><span class="line">		bzero(buf, BUFSIZ);</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;&gt;&quot;</span>);</span><br><span class="line">		<span class="keyword">if</span> (fgets(buf, BUFSIZ - <span class="number">1</span>, <span class="built_in">stdin</span>) == <span class="literal">NULL</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;fgets&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.2发送数据 */</span></span><br><span class="line">		<span class="keyword">if</span>(sendto(socket_fd, buf, <span class="built_in">strlen</span>(buf), <span class="number">0</span>, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;sendto&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.3判断是否需要退出 */</span></span><br><span class="line">		<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span> (<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">printf</span> (<span class="string">&quot;Client is exiting!\n&quot;</span>);</span><br><span class="line">			<span class="keyword">break</span>;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 7.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s boardcast_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t boardcast_ip: boardcast ip address(x.x.x.255 or 255.255.255.255)&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="6-3-Makefile"><a href="#6-3-Makefile" class="headerlink" title="6.3 Makefile"></a><font size=3>6.3 <code>Makefile</code></font></h3><p>由于需要生成两个可执行程序，自己输命令有些繁琐，这里使用<code>make</code>来进行。</p>
<details class="folding-tag" blue><summary> 点击查看 Makefile 文件 </summary>
              <div class='content'>
              <figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">## =====================================================</span></span><br><span class="line"><span class="comment"># Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"># File name: Makefile</span></span><br><span class="line"><span class="comment"># Author   : fanhua</span></span><br><span class="line"><span class="comment"># Description: Makefile文件</span></span><br><span class="line"><span class="comment">## ======================================================</span></span><br><span class="line"><span class="comment"># </span></span><br><span class="line">CC = gcc</span><br><span class="line"></span><br><span class="line">DEBUG = -g -O2 -Wall</span><br><span class="line">CFLAGS += <span class="variable">$(DEBUG)</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># 所有.c文件去掉后缀</span></span><br><span class="line">TARGET_LIST = $&#123;patsubst %.c, %, $&#123;wildcard *.c&#125;&#125; </span><br><span class="line">all : <span class="variable">$(TARGET_LIST)</span></span><br><span class="line"></span><br><span class="line">%.o : %.c</span><br><span class="line">	<span class="variable">$(CC)</span> <span class="variable">$(CFLAGS)</span> -c <span class="variable">$&lt;</span> -o <span class="variable">$@</span></span><br><span class="line"></span><br><span class="line"><span class="meta"><span class="keyword">.PHONY</span>: all clean clean_o clean_out</span></span><br><span class="line">clean : clean_o clean_out</span><br><span class="line">	@rm -vf <span class="variable">$(TARGET_LIST)</span> </span><br><span class="line">	</span><br><span class="line">clean_o :</span><br><span class="line">	@rm -vf *.o</span><br><span class="line">	</span><br><span class="line">clean_out :</span><br><span class="line">	@rm -vf *.out</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="6-4-测试结果"><a href="#6-4-测试结果" class="headerlink" title="6.4 测试结果"></a><font size=3>6.4 测试结果</font></h3><p>我们执行以下命令编译链接程序，生成两个可执行文件：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">make</span><br></pre></td></tr></table></figure>

<p>然后会有如下提示，并生成两个可执行文件吗，分别为服务器端程序<code>server</code>和客户端程序<code>client</code>：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc -g -O2 -Wall    client.c   -o client</span><br><span class="line">gcc -g -O2 -Wall    server.c   -o server</span><br></pre></td></tr></table></figure>

<p>对于服务器端，我们执行以下命令启动服务器进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./server 0.0.0.0 5001 # 允许监听所有网卡IP及端口</span><br></pre></td></tr></table></figure>

<p>对于客户端，我们执行以下命令启动客户端进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">./client 192.168.10.255 5001  # 连接到本地一块网卡的IP</span><br><span class="line">./client 192.168.239.255 5001 # 连接到本地一块网卡的IP</span><br></pre></td></tr></table></figure>

<p>然后我们就会看到如下现象：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-10-%E5%B9%BF%E6%92%AD%E4%B8%8E%E5%A4%9A%E6%92%AD/img/image-20220705174101472.png" alt="image-20220705174101472" style="zoom:50%;" />

<h1 id="二、组播编程"><a href="#二、组播编程" class="headerlink" title="二、组播编程"></a><font size=3>二、组播编程</font></h1><h2 id="1-组播的概念"><a href="#1-组播的概念" class="headerlink" title="1. 组播的概念"></a><font size=3>1. 组播的概念</font></h2><p>我们知道单播方式只能发给一个接收方。广播方式发给所有的主机，而过多的广播会大量占用网络带宽，造成广播风暴，影响正常的通信。而<strong>组播</strong>(又称为<strong>多播</strong>)是一种折中的方式，只有加入某个多播组的主机才能收到数据。</p>
<p>组播指的是报文从一个源发出，被转发到一组特定的接收者，相同的报文在每条链路上最多有一份。相较于传统的单播和广播，组播可以有效地节约网络带宽、降低网络负载，所以被广泛应用于<code>IPTV</code>、实时数据传送和多媒体会议等网络业务中。</p>
<p>组播方式既可以发给多个主机，又能避免象广播那样带来过多的负载(每台主机要到传输层才能判断广播包是否要处理)</p>
<h2 id="2-组播地址"><a href="#2-组播地址" class="headerlink" title="2. 组播地址"></a><font size=3>2. 组播地址</font></h2><h3 id="2-1IPv4组播地址"><a href="#2-1IPv4组播地址" class="headerlink" title="2.1IPv4组播地址"></a><font size=3>2.1<code>IPv4</code>组播地址</font></h3><p><code>IANA</code>将<code>D</code>类地址空间分配给<code>IPv4</code>组播使用。<code>IPv4</code>地址一共<code>32</code>位，<code>D</code>类地址最高<code>4</code>位为<code>1110</code>，地址范围从<code>224.0.0.0</code>到<code>239.255.255.255</code>，具体分类及含义如下：</p>
<table>
    <tr><td align="left" width=300px>224.0.0.0 ~ 224.0.0.255</td><td align="left">永久组地址。IANA为路由协议预留的IP地址（也称为保留组地址），用于标识一组特定的网络设备，供路由协议、拓扑查找等使用，不用于组播转发。</td></tr>
    <tr><td align="left" width=300px>224.0.1.0 ~ 231.255.255.255<br>233.0.0.0 ~ 238.255.255.255</td><td align="left">ASM组地址，全网范围内有效。</td></tr>
    <tr><td align="left" width=300px>232.0.0.0 ~ 232.255.255.255</td><td align="left">缺省情况下的的SSM组地址范围，全网范围内有效。</td></tr>
    <tr><td align="left" width=300px>239.0.0.0 ~ 239.255.255.255</td><td align="left">本地管理组地址，仅在本地管理域内有效。在不同的管理域内重复使用相同的本地管理组地址不会导致冲突。</td></tr>
</table>


<h3 id="2-2-IPv6组播地址"><a href="#2-2-IPv6组播地址" class="headerlink" title="2.2 IPv6组播地址"></a><font size=3>2.2 <code>IPv6</code>组播地址</font></h3><p><code>IPv6</code>地址长度是<code>128</code>位，<code>IPv6</code>组播地址格式如图所示：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-10-%E5%B9%BF%E6%92%AD%E4%B8%8E%E5%A4%9A%E6%92%AD/img/image-20220705193345376.png" alt="image-20220705193345376" style="zoom:50%;" />

<ul>
<li><code>IPv6</code>组播地址总是以<code>FF</code>开头，高<code>8</code>位取值为<code>1111 1111</code>。</li>
<li><code>flags</code>字段（<code>4</code>位）用来标识组播地址的状态。例如取值为<code>0</code>表示保留组地址，取值为<code>1</code>或<code>2</code>表示<code>ASM</code>范围内的组播地址，取值为<code>3</code>表示<code>SSM</code>范围内的组播地址。</li>
<li><code>scope</code>字段（<code>4</code>位）用来标识组播组的应用范围，指示组播组应用范围是只包含同一本地网络、同一站点、同一机构中的节点，还是包含全球地址空间内的任何节点。</li>
<li><code>Group ID</code>（<code>112</code>位）组播组标识符，用在由<code>scope</code>字段所指定的范围内标识组播组。</li>
</ul>
<table>
    <tr><td align="left" width=300px>FF0x::/32</td><td align="left">保留组地址。</td></tr>
    <tr><td align="left" width=300px>FF1x::/32(x不能是1或者2)<br>FF2x::/32(x不能是1或者2)</td><td align="left">ASM组地址，全网范围内有效。</td></tr>
    <tr><td align="left" width=300px>FF3x::/32(x不能是1或者2)</td><td align="left">缺省的SSM组地址范围，全网范围内有效。</td></tr>
</table>


<h2 id="3-组播编程步骤"><a href="#3-组播编程步骤" class="headerlink" title="3. 组播编程步骤"></a><font size=3>3. 组播编程步骤</font></h2><div class="tabs" id="tabname2"><ul class="nav-tabs"><li class="tab active"><a href="#tabname2-1">组播发送</a></li><li class="tab"><a href="#tabname2-2">组播接收</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname2-1"><ul>
<li>创建用户数据报套接字，注意<code>soclet()</code>函数第二个参数要写为<code>SOCK_DGRAM</code>。</li>
<li>接收方地址指定为组播地址。</li>
<li>指定端口信息。</li>
<li>发送数据包。</li>
</ul></div><div class="tab-pane" id="tabname2-2"><ul>
<li>创建用户数据报套接字，注意<code>soclet()</code>函数第二个参数要写为<code>SOCK_DGRAM</code>。</li>
<li>加入多播组。</li>
<li>绑定本机<code>IP</code>地址和端口，绑定的端口必须和发送方指定的端口相同。</li>
<li>等待接收数据。</li>
</ul></div></div></div>

<h2 id="4-两个socket选项"><a href="#4-两个socket选项" class="headerlink" title="4. 两个socket选项"></a><font size=3>4. 两个<code>socket</code>选项</font></h2><p>这里我们需要将接收端加入到多播组中，所以我们可能会用到两个<code>socket</code>的选项，<code>IP_ADD_MEMBERSHIP</code>*和<code>IP_DROP_MEMBERSHIP</code>，这两个都属于<code>IPPROTO_IP</code>层。</p>
<ul>
<li><p><code>IP_ADD_MEMBERSHIP</code>表示加入一个多播组；</p>
</li>
<li><p><code>IP_DROP_MEMBERSHIP</code>表示退出一个多播组；</p>
</li>
</ul>
<p>我们可以使用<code>man 7 ip</code>命令查看帮助手册的<code>Socket options</code>部分来查看这两个选项的详细说明。这两个选项对应的数据类型都是<code>struct ip_mreq</code>类型的结构体变量，该结构体原型如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">ip_mreq</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">in_addr</span> <span class="title">imn_multiaddr</span>;</span>      <span class="comment">/* 加入或者退出的广播组IP地址 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">in_addr</span> <span class="title">imr_interface</span>;</span>      <span class="comment">/* 加入或者退出的网络接口IP地址 */</span></span><br><span class="line">&#125;;</span><br><span class="line"></span><br></pre></td></tr></table></figure>

<p>使用示例如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">define</span> MULTICAST_IP <span class="string">&quot;235.10.10.3&quot;</span></span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">ip_mreq</span> <span class="title">mreq</span>;</span></span><br><span class="line">bzero(&amp;mreq, <span class="keyword">sizeof</span>(mreq));</span><br><span class="line">mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_IP);</span><br><span class="line">mreq.imr_interface.s_addr = htonl(INADDR_ANY);</span><br><span class="line">setsockopt(socket_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &amp;mreq, <span class="keyword">sizeof</span>(mreq));</span><br></pre></td></tr></table></figure>

<h2 id="5-使用实例"><a href="#5-使用实例" class="headerlink" title="5. 使用实例"></a><font size=3>5. 使用实例</font></h2><h3 id="5-1-server服务器端"><a href="#5-1-server服务器端" class="headerlink" title="5.1 server服务器端"></a><font size=3>5.1 <code>server</code>服务器端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: server.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: server服务器端——组播(UDP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>      <span class="comment">/* perror */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>     <span class="comment">/* exit atoi */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>      <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span>  <span class="comment">/* socket           bind listen recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span> <span class="comment">/* socket inet_addr bind listen recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;strings.h&gt;</span>    <span class="comment">/* bzero */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span>  <span class="comment">/* htons  inet_addr inet_pton */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span> <span class="comment">/* ntohs  inet_addr inet_ntop*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>     <span class="comment">/* close */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>     <span class="comment">/* strlen strcat*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 1.参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">4</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 2.创建套接字，得到socket描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span>((socket_fd = socket(AF_INET, SOCK_DGRAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)<span class="comment">/* SOCK_STREAM,使用TCP协议 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 3.网络属性设置 */</span></span><br><span class="line">	<span class="comment">/* 3.1允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line">	<span class="comment">/* 3.2加入多播组 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">ip_mreq</span> <span class="title">mreq</span>;</span></span><br><span class="line">	bzero(&amp;mreq, <span class="keyword">sizeof</span>(mreq));</span><br><span class="line">	mreq.imr_multiaddr.s_addr = inet_addr(argv[<span class="number">3</span>]);</span><br><span class="line">	mreq.imr_interface.s_addr = inet_addr(argv[<span class="number">1</span>]);</span><br><span class="line">	setsockopt(socket_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,&amp;mreq, <span class="keyword">sizeof</span>(mreq));</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 4.将套接字与指定端口号和IP进行绑定 */</span></span><br><span class="line">	<span class="comment">/* 4.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>));  <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;    <span class="comment">/* 协议族, IPv4 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port);  <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* 填充IP地址,INADDR_ANY表示允许监听任意IP,但是它其实是(in_addr_t) 0x00000000 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 4.2绑定 */</span></span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;Multicast server starting....OK(UDP)!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 5.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="comment">/* 5.2客户端IP地址及端口号获取的相关变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">cin</span>;</span>          <span class="comment">/* 用于存储成功连接的客户端的IP信息 */</span></span><br><span class="line">	<span class="type">socklen_t</span> addrlen = <span class="keyword">sizeof</span>(<span class="built_in">cin</span>);</span><br><span class="line">	<span class="type">char</span> ipv4_addr[<span class="number">16</span>];</span><br><span class="line">	<span class="comment">/* 5.2数据读写相关变量 */</span></span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="comment">/* 6.数据读写 */</span></span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 6.1接收来自客户端的数据 */</span></span><br><span class="line">		bzero(buf, BUFSIZ);</span><br><span class="line">		<span class="keyword">if</span>(recvfrom(socket_fd, buf, BUFSIZ<span class="number">-1</span>, <span class="number">0</span>,(<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">cin</span>, &amp;addrlen ) &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;recvfrom&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.2打印客户端的IP信息 */</span></span><br><span class="line">		<span class="keyword">if</span> (!inet_ntop (AF_INET, (<span class="type">void</span> *) &amp;<span class="built_in">cin</span>.sin_addr, ipv4_addr, <span class="keyword">sizeof</span> (<span class="built_in">cin</span>)))</span><br><span class="line">		&#123;</span><br><span class="line">			perror (<span class="string">&quot;inet_ntop&quot;</span>);</span><br><span class="line">			<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;Recived from(%s:%d), data:%s&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port), buf);</span><br><span class="line">		<span class="comment">/* 6.3判断是否需要退出 */</span></span><br><span class="line">		<span class="keyword">if</span>(!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span>(<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">printf</span> (<span class="string">&quot;Client(%s:%d) is exiting!\n&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port));</span><br><span class="line">			<span class="comment">// break;</span></span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 7.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;\n%s serv_ip serv_port Multicast_ip&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;\n\t serv_port: server port(&gt;5000)&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;\n\t Multicast_ip: Multicast ip address(between 224~239 segment. eg. 235.10.10.3)\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;\n\t Attention: The serv_ip address must be the IP address of the local nic or 0.0.0.0 \n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="5-2-client客户端"><a href="#5-2-client客户端" class="headerlink" title="5.2 client客户端"></a><font size=3>5.2 <code>client</code>客户端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: cilent.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: client客户端程序——组播(UDP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>     <span class="comment">/* perror fgets */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>    <span class="comment">/* exit atoi*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>     <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>    <span class="comment">/* write close */</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span> <span class="comment">/* socket           recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span><span class="comment">/* socket inet_addr recvfrom sendto */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span><span class="comment">/* inet_addr */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span> <span class="comment">/* inet_addr inet_pton htonl*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>   <span class="comment">/* bzero strncasecmp strlen */</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 主函数 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 1.参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">3</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 2.打开套接字，得到套接字描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span> ((socket_fd = socket(AF_INET, SOCK_DGRAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 3.网络属性设置 */</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 4.连接服务器 */</span></span><br><span class="line">	<span class="comment">/* 4.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="comment">/* 客户端的 argv[1] 需要与系统的IP一致 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;Multicast client staring...OK(UDP)!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 5.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="comment">/* 6.数据读写 */</span></span><br><span class="line">	<span class="keyword">while</span> (<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 6.1标准输入获取发送数据 */</span></span><br><span class="line">		bzero(buf, BUFSIZ);</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;&gt;&quot;</span>);</span><br><span class="line">		<span class="keyword">if</span> (fgets(buf, BUFSIZ - <span class="number">1</span>, <span class="built_in">stdin</span>) == <span class="literal">NULL</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;fgets&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.2发送数据 */</span></span><br><span class="line">		<span class="keyword">if</span>(sendto(socket_fd, buf, <span class="built_in">strlen</span>(buf), <span class="number">0</span>, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;sendto&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 6.3判断是否需要退出 */</span></span><br><span class="line">		<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span> (<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">printf</span> (<span class="string">&quot;Client is exiting!\n&quot;</span>);</span><br><span class="line">			<span class="keyword">break</span>;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 7.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s Multicast_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t Multicast_ip: boardcast ip address(between 224~239 segment. eg. 235.10.10.3)&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="5-3-Makefile"><a href="#5-3-Makefile" class="headerlink" title="5.3 Makefile"></a><font size=3>5.3 <code>Makefile</code></font></h3><p>由于需要生成两个可执行程序，自己输命令有些繁琐，这里使用<code>make</code>来进行。</p>
<details class="folding-tag" blue><summary> 点击查看 Makefile 文件 </summary>
              <div class='content'>
              <figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">## =====================================================</span></span><br><span class="line"><span class="comment"># Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"># File name: Makefile</span></span><br><span class="line"><span class="comment"># Author   : fanhua</span></span><br><span class="line"><span class="comment"># Description: Makefile文件</span></span><br><span class="line"><span class="comment">## ======================================================</span></span><br><span class="line"><span class="comment"># </span></span><br><span class="line">CC = gcc</span><br><span class="line"></span><br><span class="line">DEBUG = -g -O2 -Wall</span><br><span class="line">CFLAGS += <span class="variable">$(DEBUG)</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># 所有.c文件去掉后缀</span></span><br><span class="line">TARGET_LIST = $&#123;patsubst %.c, %, $&#123;wildcard *.c&#125;&#125; </span><br><span class="line">all : <span class="variable">$(TARGET_LIST)</span></span><br><span class="line"></span><br><span class="line">%.o : %.c</span><br><span class="line">	<span class="variable">$(CC)</span> <span class="variable">$(CFLAGS)</span> -c <span class="variable">$&lt;</span> -o <span class="variable">$@</span></span><br><span class="line"></span><br><span class="line"><span class="meta"><span class="keyword">.PHONY</span>: all clean clean_o clean_out</span></span><br><span class="line">clean : clean_o clean_out</span><br><span class="line">	@rm -vf <span class="variable">$(TARGET_LIST)</span> </span><br><span class="line">	</span><br><span class="line">clean_o :</span><br><span class="line">	@rm -vf *.o</span><br><span class="line">	</span><br><span class="line">clean_out :</span><br><span class="line">	@rm -vf *.out</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="5-4-测试结果"><a href="#5-4-测试结果" class="headerlink" title="5.4 测试结果"></a><font size=3>5.4 测试结果</font></h3><p>我们执行以下命令编译链接程序，生成两个可执行文件：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">make</span><br></pre></td></tr></table></figure>

<p>然后会有如下提示，并生成两个可执行文件吗，分别为服务器端程序<code>server</code>和客户端程序<code>client</code>：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc -g -O2 -Wall    client.c   -o client</span><br><span class="line">gcc -g -O2 -Wall    server.c   -o server</span><br></pre></td></tr></table></figure>

<p>对于服务器端，我们执行以下命令启动服务器进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">./server 0.0.0.0 5001 235.10.10.3 # 允许监听所有网卡IP及端口</span><br><span class="line">./server 0.0.0.0 5001 235.10.10.3 # 允许监听所有网卡IP及端口</span><br></pre></td></tr></table></figure>

<p>对于客户端，我们执行以下命令启动客户端进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">./client 235.10.10.3 5001  # 发送数据到组播IP</span><br><span class="line">./client 235.10.10.3 5001  # 发送数据到组播IP</span><br></pre></td></tr></table></figure>

<p>然后我们就会看到如下现象：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-10-%E5%B9%BF%E6%92%AD%E4%B8%8E%E5%A4%9A%E6%92%AD/img/image-20220706055721882.png" alt="image-20220706055721882" style="zoom:50%;" />

<p>这里我们可以七佛那个两个服务器，看会不会都能收到数据，服务器启动时，命令重要加入组播地址，用于让服务器加入多播组，客户端直接想组播地址发送数据即可。</p>

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